Dozens of genes previously thought to share similar functions across different species were found to be unique in humans only. According to the researchers from the University of Toronto‘s Terrence Donnelly Centre for Cellular & Biomolecular Research, the unique genes may hold the key to the evolution of humans.
In the team’s research paper published in the journal Nature Genetics, they described the genes as the ones responsible for coding a class of protein called transcription factors (TFs). TFs are known to control gene activity. They recognize DNA motifs or distinct snippets of the DNA code, using them as “landing sites to bind the DNA and turn the genes on or off.”
Past studies have reported that TFs, which appears similar across different organisms, also bind the same motifs in various species including fruit flies and humans. However, the Toronto-based researchers claimed that it was not the case.
Unique Genes in Humans
The Canadian researchers reportedly used a new computational method to predict the motif sequences that each TF binds in various species more accurately. The results of their observation suggest that some sub-classes of TFs are more functionally diverse than previously believed.
To accomplish this, they developed a software capable of identifying similarities between the DNA binding regions related to the TFs ability to bind similar or different DNA motifs. Unlike current methods, the team’s software automatically puts higher values on amino acids or parts of the whole region that have direct contact with the DNA.
Meaning, two TFs, that look similar to each other, are more likely to bind different DNA motifs if their amino acids differ in positions. The researchers used the method to compare and match the TFs of different species and were surprised to discover that human TFs said to be similar to those of fruit flies identify different DNA motifs, making them unique genes.
The team’s findings contradicted a previous study claiming that the TFs of both humans and fruit flies bind the same DNA motif sequences.
“There is this idea that has persevered, which is that the TFs bind almost identical motifs between humans and fruit flies. And while there are many examples where these proteins are functionally conserved, this is by no means to the extent that has been accepted.”
~Professor Timothy Hughes, Donnelly Centre for Cellular and Biomolecular Research
In fact, even between humans and chimpanzees, which have 99 percent identical genomes, there are dozens of TFs that recognize different motifs in the two species. This reportedly impacts the expression of hundreds of different genes.
Sam Lambert, one of the researchers from the University of Toronto and a co-author of the paper, said:
“Even between closely related species, there’s a non-negligible portion of TFs that are likely to bind new sequences. This means they are likely to have novel functions by regulating different genes, which may be important for species differences.”
The unique genes allegedly belong to a rapidly evolving class of C2H2 zinc finger TFs which use zinc ions to bind human DNA.
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